Contents

Getting Started

During package upgrades or removal Pacman will inform you of files (usually configurations in /etc) that are being installed with a .pacnew extension or backed up with a .pacsave extension.

A .pacnew file may be created during a package upgrade (pacman -Syu, pacman -Su or pacman -U) to avoid overwriting a file which already exists and was previously modified by the user. When this happens a message like the following will appear in the output of pacman:

warning: /etc/pam.d/usermod installed as /etc/pam.d/usermod.pacnew

A .pacsave file may be created during a package removal (pacman -R), or by a package upgrade (the package must be removed first). When the pacman database has record that a certain file owned by the package should be backed up it will create a .pacsave file. When this happens pacman outputs a message like the following:

warning: /etc/pam.d/usermod saved as /etc/pam.d/usermod.pacsave

These files require manual intervention from the user and it is good practice to handle them right after every package upgrade or removal. If left unhandled, improper configurations can result in improper function of the software, or the software being unable to run altogether.

Package backup files

A package's PKGBUILD file specifies which files should be preserved or backed up when the package is upgraded or removed. For example, the PKGBUILD for pulseaudio contains the following line:

Types Explained

The different types of *.pac* files.

.pacnew

For each backup file in a package being upgraded, pacman cross-compares three md5sums generated from the file's contents: one sum for the version originally installed by the package, one for the version currently in the filesystem, and one for the version in the new package. If the version of the file currently in the filesystem has been modified from the version originally installed by the package, pacman cannot know how to merge those changes with the new version of the file. Therefore, instead of overwriting the modified file when upgrading, pacman saves the new version with a .pacnew extension and leaves the modified version untouched.

Going into further detail, the 3-way MD5 sum comparison results in one of the following outcomes:

original = X, current = X, new = X

All three versions of the file have identical contents, so overwriting is not a problem. Overwrite the current version with the new version and do not notify the user. (Although the file contents are the same, this overwrite will update the filesystem's information regarding the file's installed, modified, and accessed times, as well as ensure that any file permission changes are applied.)

original = X, current = X, new = Y

The current version's contents are identical to the original's, but the new version is different. Since the user has not modified the current version and the new version may contain improvements or bugfixes, overwrite the current version with the new version and do not notify the user. This is the only auto-merging of new changes that pacman is capable of performing.

original = X, current = Y, new = X

The original package and the new package both contain exactly the same version of the file, but the version currently in the filesystem has been modified. Leave the current version in place and discard the new version without notifying the user.

original = X, current = Y, new = Y

The new version is identical to the current version. Overwrite the current version with the new version and do not notify the user. (Although the file contents are the same, this overwrite will update the filesystem's information regarding the file's installed, modified, and accessed times, as well as ensure that any file permission changes are applied.)

original = X, current = Y, new = Z

All three versions are different, so leave the current version in place, install the new version with a .pacnew extension and warn the user about the new version. The user will be expected to manually merge any changes necessary from the new version into the current version.

.pacsave

If the user has modified one of the files specified in backup then that file will be renamed with a .pacsave extension and will remain in the filesystem after the rest of the package is removed.

.pacorig

When a file (usually a configuration found in /etc) is encountered during package installation or upgrade that does not belong to any installed package but is listed in backup for the package in the current operation, it will be saved with a .pacorig extension and replaced with the version of the file from the package. Usually this happens when a configuration file has been moved from one package to another. If such a file were not listed in backup, pacman would abort with a file conflict error.

Locating .pac* Files

Arch Linux does not provide official utilities for .pacnew files. You'll need to maintain these yourself; a few tools are presented in the next section. To do this manually, first you will need to locate them. When upgrading or removing a large number of packages, updated *.pac* files may be missed. To discover whether any *.pac* files have been installed:

Note that the log does not keep track of which files are currently in the filesystem nor of which files have already been removed.

Managing .pacnew Files

Once all existing .pacnew files have been located, the user may handle them manually using common merge tools such as vimdiff, ediff (part of emacs), meld (a GNOME GUI tool), sdiff (part of diffutils, or Kompare (a KDE GUI tool), then deleting the .pacnew files afterwards.

A few third-party utilities providing various levels of automation for these tasks are available from the community repository and the AUR.